Micrometer-gage



Patented June 9, 1885.

I K/ENTE M A m T G M T... m R F ,E. M P m W 0 m M (No Model.)

WITNEE SEE UNITED STATES PATENT rerun.

J ERREY MOFFITT, OF SOUTI-IBRIDGE, MASSACHUSETTS.

MlCROMETER-GAGE.

SPECIFICATION forming part. of Letters Patent No. 319,919, dated June 9,, 1885.

Application filed March 25, 1835.

To all whom it may concern.-

Be it known that I, J ERREY Morrrr'r, a citizen of the United States, residing at Southbridge, in the county of Worcester and State of Massachusetts, have invented certain new and useful Improvements in Micrometer Oalipers or Gages; and I declare the following to be a description of my said invention, sufficiently full, clear, and exact to enable others skilled in the art to which it appertains to make and use the same, reference being had to the accompanying drawings, which form a part of this specification.

In the construction of micrometercalipers of the class to which my invention appertains it has heretofore been the practice to form one or more slots in the cylindrical portion which surrounds the gage-screw, so that the sides of said cylinder may be sprung together for taking up the looseness or backlash occasioned by wear on the threads of said gage-screw, and these slots, being more or less open when the screw is run out, afford a passage through which dust, dirt, and fine metal filings enter to the interior of the cylinder, find lodgment upon the screw-threads, and by their gritty action greatly increase the abrasion and wear on the threads, so that in a comparatively short time the perfection and accuracyof the instrument is destroyed, as a slight variation or irregularity will throw the indicatiug-lines out of proper relation, and thus render the tool practically worthless for denoting the very fine measurements and gagings for which it is intended.

The objects of my present invention are, to afford facilities for tightening the grip upon the gagescrew threads, and to avoid the necessity of a split or division in the cylinder or part of the frame which surrounds said gage-screw,thus obviating the liability of dust, dirt, or filings entering and wearing out the threads; also, to provide a construction of the step-screw that will permit of said screw being more accurately maintained in exact align-- ment with the gage'screw under all conditions of adjustment, so that the faces of the two screws will stand in accurate relation to each other when turned from their original positions. These objects I attain by constructing the instrument in the peculiar manner hereinafter described and claimed.

(No model.)

In the drawings, Figure l is a side view of a micrometer caliper or gage embracing my invention. Fig. 2 is a longitudinal section through the frame and screw cap or sheath. Fig. 3 shows a side and end view of the adjusting ring ornut, and Fig. 4 is a modifica- I tion of the same.

In referring to parts, A denotes the U -shaped frame provided with the cylindrical extension A, through which the micrometer-gage screw B is arranged. Said cylinder is formed solid or without the-usual slot or division, and has within its outer end a slightly-tapered female thread at a. dinary form, with a spindle or unthreaded portion guided in the frame at f, and with an overhanging cap or sheath, E, that covers the cylinder A in the usual manner, and which is milled at the head to facilitate turning the screw. The indicating-graduations are formed on the side of the cylinder A and on the end of the sheath E in the usual manner. A conoidal nut or thimblc, D, having screw-threads on its exterior and interior, and having a slit at one side, as at (Z, is fitted within the threaded end of the cylinder A around the gage-screw B, the external thread of said nut fitting the thread of the cylinder, and the internal thread of said nut fitting the thread of the screw B. Both threads of the nut are of the same pitch or number of threads to the inch. The up per end of the nut that projects from the cylinder is milled, as at c, or fitted so that it can be turned conveniently when the outer cylindrical sheath or cap, E, is raised or run out. By turning said tapered nut D down into the tapered end of the cylinder the diameter of the thimble or nut is contracted to take up the backlash or wear, and cause it to grip more tightly upon the screw B, and vice versa. The sheath E fits closely the exterior of the cylinder A, and the smooth spindle of the screw closely the opening in the frame at f, and as there is no slot in the side of the cylinder the screw-threads are completely protected from the entrance of dirt. XVhen the thread of the screw B and nut D become worn out beyond the limit of adjustment, so as to occasion inaccuracy in the gage, the instrument can be renewed by simply replacing the nut or thimble D with a new nut of slightly greater thickness, thus avoiding the necessity of procuring The gage screw B is made of oran entire new-instrument. The step-screw I is made with a shoulder, as indicated,the point 'i being turned down cylindrical to a size corresponding with the smooth part of the screw B, and the threaded portion 1" being of larger diameter. The hole J through thestep' of the frame A, is bored out to correspond in alignment and axial relation with the hole f. The lower part of the hole J is then counterbored, and its thread cut with a tap having a leader that extends up through the holef. It sometimes becomes necessary to rectify the gage by setting the step or anvil I slightlyin or out. If the step is simply screwed through the frame and depends on the screw-thread for keepingits end in central alignment, it isvery liable-to be finished with a greater or less degree of eccentricity or slight inclination, so

that the slight turning of the step-screw I, instead of rectifying the instrument, simply throwsits point out of position. By the construction herein shown the part of the hole whichretai-ns the point i central is made smooth'and cylindrieal'and in accurate aligninent'with the hole in which the mierometerspindle B moves, so that ifthe step I isturned theaxis'of both the openingsf and J, will have no chance to exert an eccentric action tendingto throw the point of the step to. one

side .of its original position or its face outof.

proper relation with-the face of the spindle B, but will simply move the part in and out indirection exactly coincident with the axes of the parts B and'I, and after the meeting faces or points of thetwo screws 'B and-I have bzen-rquared to each other they are not subjectto deviationsfrom accuracy by the turning of said screw on its axis togive adjustment of distance between the points.

As a modification in construction, the nut .or.ring D and interior of the cylinder A may be made with a straight threaded portion, and a smooth conical part, m, below the thread, as indicated in Fig. 4. I prefer, however, the form first above described.

\Vhat I claim as of my invention,and desire to secure by Letters Patent, is-- l 1. The tapered nut or ring D, externally and internally screw-threaded, and having the slot (1, in combination with the gage-screw B and the frame A,havingthecylindrical internallythreaded: extension A, substantially asset forth.

2. The combination, with the frame A-a-nd micrometer-gage screw B, of the screw I, hav ing the reduced portion 1' andthreaded portion i, fitted into thestep of the frame in the mannershown and described.

3. In a micrometer caliper or gage, the combination of the gaging-screw B, havingthe smoothguiding portion and threaded portion, l the U-shaped frame A, with the internallythreaded unslotted cylindrical extension A, the conoidal double-threaded thimblenut D,

supporting said'screw within the cylindricalextension, and the'step-screw I, having the reduced'portionw' and the threaded portion Ti, fitted' to said frame, substantially as set forth.

\Vitness my hand this 19th day of March, A. D4885.-

J E RREY MOFFITT.

\Vitnesses:

GEORGE W. COREY, G. D; MONROE. 

